1. Technical Field
The invention relates to conveyor belts and in particular to an improved guiding system for mechanically maintaining a conveyor belt in accurate alignment without using the dynamics of the belt for guidance.
2. Background Information
Conveyor belts are used in many applications for transporting materials between load and unload stations. These conveyors consist of various types of flexible or rigid belts on which the material being conveyed is supported as the belt moves over a plurality of spaced rolls, slide plates, or other supporting structures located between the load and unload stations. Many conveyors use flexible endless belts formed of various fabrics which move around head and tail pulleys, one of which is power driven, and are supported on both the top delivery and bottom return levels of the belt by spaced rolls or slide plates which usually extend between side support structures.
It is desirable to maintain the belt in alignment between the adjacent supporting structures, such as vertical posts, to prevent the belt from wandering or moving transversely across the rolls or slide plates as the belt is driven in a longitudinal direction by the head pulley. One of the most common means of maintaining the belts in alignment is by using the dynamics of the belts themselves by engaging the moving belts with crowned pulleys, side guide rolls, or other mechanical mechanisms which engage the belt to maintain it in accurate alignment.
It is desirable for certain applications to accurately maintain the belt tracking so that the material being conveyed thereby is accurately delivered at the unload station. For example, in the transporting of various elastomeric strips of material in the manufacture of vehicle tires, air springs, and like articles, the strip material must be accurately delivered to a wind-up reel at the unload station. If the belt "wanders" or "walks" as it moves between the load and unload station, the strip material will be incorrectly wound on the wind-up reel, which when subsequently discharged, will provide inaccurate delivery of the required material strips used in the particular manufacturing process.
Thus, it is extremely critical for certain manufacturing operations that the conveyor accurately tracks or moves between the load and unload stations so that the material conveyed thereby is accurately delivered at the unload station. It has been found that by using the dynamics of the belt itself for guiding, it does not provide the desired accuracy for certain applications.
Prior art conveyors using various types of guiding systems are shown in the various patents discussed below.
U.S. Pat. No. 702,408 discloses a conveyor structure which has a trolley-track positioned in a frame which serves as a guide to trolley wheels to prevent lateral displacement of slats which form the supporting conveyor. The trolley is secured to every alternate bracket and two trolley wheels are pivotly mounted on chains.
U.S. Pat. No. 809,827 discloses a conveyor wherein generally U-shaped supporting elements are located on either side of the conveyor track. Rollers are positioned to facilitate movement of flexible material and are essentially separate elements from the conveyor material itself.
U.S. Pat. No. 1,026,617 discloses a conveyor comprising a plurality of slats to which rollers are attached on opposite sides thereof which then are attached via apertures on opposite sides of each of the slats.
U.S. Pat. No. 1,708,357 discloses a conveyor
having a plurality of transversely extending sleeves which are movably supported on rolls by connecting links. The rolls move along horizontal tracks.
U.S. Pat. No. 1,758,397 discloses an endless conveyor wherein wheels move along parallel tracks and guides are secured to the tracks to keep the wheels aligned. Conveyor plates are mounted on chains, the ends of which are attached to links connected by pins to which the rollers or wheels are rotatably mounted.
U.S. Pat. No. 2,558,832 discloses a conveyor mechanism wherein rollers move on tracks, and in which brackets are attached to bars with rollers indirectly being attached to slats to facilitate movement of the conveyor, including such slats along the supporting structure.
U.S. Pat. No. 2,694,484 discloses an endless conveyor comprising plates on which rollers are attached by appropriate brackets.
Although the conveyor mechanisms and alignment features of the conveyors disclosed in the patents set forth above and in other known conveyor constructions do provide some solution to the conveyor belt alignment problem, none of these patents are believed to disclose a conveyor having a flexible belt with trolley wheels or other type of slide mechanism attached in a stationary fashion on one side of the belt and in a spring biased fashion on the other side of the belt, for maintaining accurate alignment or tracking of the conveyor belt as in my invention, which is described in detail below and set forth in the appended claims.